The present application relates to load shift transmissions with stepless hydrostatic gearing, i.e. steplessly working hydrostatic-mechanical load shift transmissions, which are advantageously suitable for motor vehicles since they are steplessly adjustable over a wide range, and in addition have good efficiency. The relatively large adjustment range permits the operation of combustion-power engines on advantageous performance lines. Such lines can be, for example, the curve for minimal fuel consumption or a line for a good acceleration characteristic.
FIG. 8 of EP 0 302 188 A1 shows a hydrostatic-mechanical load shift transmission with a five-shaft planetary gear transmission, which consists of three planetary steps respectively with the members sun gear 1', planet gear carrier s', and ring gear 2', next, sun gear 1", planet gear carrier s", and ring gear 2" as well as sun gear 1'", planet gear carrier s'", and ring gear 2'". The coupled element members 2', 2" and s'" function as drive shaft 1, s' and s" as the slow-running coupling shaft, the ring gear 2'" as the fast-running coupling shaft, the sun gear 1' as the connection shaft for the constant-volume displacement machine b, and the joined-together sun gears 1" and 1'" as the coupling shaft for the hydrostatic-mechanical startup.
WO 89/09899 (PTC/EP 89/00348) describes a hydrostatic-mechanical load shift transmission with a five-shaft planetary gear transmission, to which likewise belong three coupled planetary steps, namely the step with sun gear 17, planet gear carrier 12, and ring gear 20, next, the step with sun gear 16, planet gear carrier 19, and ring gear 14, and finally the step with sun gear 22, planet gear carrier 24, and ring gear 25. To the drive shaft pertain the joined element, planet gear carrier 12 and ring gear 14, to the slow-running coupling shaft the coupled elements, ring gear 20 and planet gear carrier 24, to the fast-running coupling shaft the joined sun gears 17 and 22, to the connection of the constant-volume displacement machine 7 the sun gear 16, and finally to the coupling shaft for the hydrostatic-mechanical startup the ring gear 25.
The above-described five-shaft planetary gear transmissions of the hydrostatic-mechanical load shift transmissions are built relatively in a long length and expensively.
The invention thus poses as its problem, to suggest a five-shaft planetary gear transmissions for load shift transmissions with stepless hydrostatic-mechanical gearing, consisting of three joined planetary steps, and having a simplified construction.